Combination with storage tank
In accordance with the relevant Austrian laws governing energy
technology, which are based on Art. 15a B-VG “Agreement on protective
measures for small furnaces” dated November 1994, no buffer storage
tank is required on manually fed biomass boilers that have been
positively tested at both rated load and partial load (below 50% of rated
load) to ensure they adhere to the emissions limits specified in that
agreement.
Germany has specified its own emissions limits in the “First Ordinance
on Implementation of the Federal Emissions Control Act (1st BImSchV)”.
Provided that commissioning is carried out by our customer services or
an authorised partner company, it can be assumed that these
requirements will also be complied with under partial load conditions in
accordance with § 6 (3) of the 1st BImSchV. This means that the
complete range of firewood boilers can be used in Germany without
requiring a mandatory buffer storage tank.
Combining the system with a buffer storage tank does however offer
significant advantages when using a firewood boiler, such as better
utilisation of the fuel, more user-friendly operation in terms of reloading
intervals (which means the greatest possible independence from
instantaneous heating requirements), and less soiling of the boiler and
flue gas system. In addition to the above, as the manufacturer of the
boiler we have to advise on how the heat generated can be dissipated.
This is because compliance with the emissions limits and minimum level
of efficiency at a minimum heat output of 30% of the rated heat output,
as specified in Section 4.2.5 or EN 303-5, has not been demonstrated
for all variants of the system.
The opportunities for heat dissipation are particularly good if the central
heating system has sufficient capacity for heat uptake, for example
through underfloor heating circuits with a suitable water volume or hot
water tanks with appropriate reserve capacity. It should also be noted
that the integral thermal discharge safety device ensures that the boiler
will operate safely even if it is overfilled or has too little load reduction.
If, however, the amount of heat that can be temporarily dissipated
within the building being heated is limited, then additional heat
dissipation can be provided by a buffer storage tank.
The recommend storage volume for each boiler is given in the technical
specifications. The specified value applies under the following
conditions: the rated heat output of the boiler corresponds to the
heating requirements of the building and a maximum of 50% of the
rated heat output can be dissipated to the building being heated under
partial load conditions.
Certain subsidy guidelines also prescribe compulsory
requirements for the installation of buffer storage tanks:
Some guidelines relate to minimum storage volume in accordance with
EN 303-5, as given in the technical specifications.
... In Austria: some subsidy guidelines of Austrian federal states
(e.g. those of the Vorarlberg state government)
... In Switzerland: The “Quality Seal for Wood Burning Systems”
scheme from Holzenergie Schweiz
